On Mon, 11 Dec 2023 16:37:38 GMT, Severin Gehwolf <[email protected]> wrote:
>> Please review this patch which adds a jlink mode to the JDK which doesn't
>> need the packaged modules being present. A.k.a run-time image based jlink.
>> Fundamentally this patch adds an option to use `jlink` even though your JDK
>> install might not come with the packaged modules (directory `jmods`). This
>> is particularly useful to further reduce the size of a jlinked runtime.
>> After the removal of the concept of a JRE, a common distribution mechanism
>> is still the full JDK with all modules and packaged modules. However,
>> packaged modules can incur an additional size tax. For example in a
>> container scenario it could be useful to have a base JDK container including
>> all modules, but without also delivering the packaged modules. This comes at
>> a size advantage of `~25%`. Such a base JDK container could then be used to
>> `jlink` application specific runtimes, further reducing the size of the
>> application runtime image (App + JDK runtime; as a single image *or*
>> separate bundles, depending on the app
being modularized).
>>
>> The basic design of this approach is to add a jlink plugin for tracking
>> non-class and non-resource files of a JDK install. I.e. files which aren't
>> present in the jimage (`lib/modules`). This enables producing a `JRTArchive`
>> class which has all the info of what constitutes the final jlinked runtime.
>>
>> Basic usage example:
>>
>> $ diff -u <(./bin/java --list-modules --limit-modules java.se)
>> <(../linux-x86_64-server-release/images/jdk/bin/java --list-modules
>> --limit-modules java.se)
>> $ diff -u <(./bin/java --list-modules --limit-modules jdk.jlink)
>> <(../linux-x86_64-server-release/images/jdk/bin/java --list-modules
>> --limit-modules jdk.jlink)
>> $ ls ../linux-x86_64-server-release/images/jdk/jmods
>> java.base.jmod java.net.http.jmod java.sql.rowset.jmod
>> jdk.crypto.ec.jmod jdk.internal.opt.jmod
>> jdk.jdi.jmod jdk.management.agent.jmod jdk.security.auth.jmod
>> java.compiler.jmod java.prefs.jmod java.transaction.xa.jmod
>> jdk.dynalink.jmod jdk.internal.vm.ci.jmod
>> jdk.jdwp.agent.jmod jdk.management.jfr.jmod jdk.security.jgss.jmod
>> java.datatransfer.jmod java.rmi.jmod java.xml.crypto.jmod
>> jdk.editpad.jmod jdk.internal.vm.compiler.jmod
>> jdk.jfr.jmod jdk.management.jmod jdk.unsupported.desktop.jmod
>> java.desktop.jmod java.scripting.jmod java.xml.jmod
>> jdk.hotspot.agent.jmod jdk.i...
>
> Severin Gehwolf has updated the pull request incrementally with two
> additional commits since the last revision:
>
> - Disallow packaged modules and run-time image link
> - Only check for existing path when not a scratch task
>
> When using a run-time image link and the initial build was produced with
> the --keep-packaged-modules option, we don't need to check existing
> paths to the location where packaged modules need to be copied. This
> breaks the --verbose output validation.
`JRTArchive::collectFiles` is the relevant code:
// add/persist a special, empty file for jdk.jlink so as to support
// the single-hop-only run-time image jlink
if (singleHop && JDK_JLINK_MODULE.equals(module)) {
files.add(createRuntimeImageSingleHopStamp());
}
-------------
PR Comment: https://git.openjdk.org/jdk/pull/14787#issuecomment-1899240758
